Sterling process engines

ABSTRACT

This device is an improvement over the conventional Stirling cycle engine where the so called &#39;&#39;&#39;&#39;hot&#39;&#39;&#39;&#39; and &#39;&#39;&#39;&#39;cold&#39;&#39;&#39;&#39; cylinders are mounted in a V-configuration. The improvement comprises the addition of a secondary heat source which cyclically adds heat to the system via a third displacement piston communicating with the regenerator.

Nov. 5, 1974 STERLING PROCESS ENGINES 8/1970 Simpson...................... 60/24 X a n e R 1 w 3,0 7 Y R SN we S m h ok me 8 H i WD O t n e V n 1 Q 7 Primary ExaminerEdgar W. Geoghegan Assistant ExaminerAllen M. Ostrager [22] Filed: May 21, 1970 [57] ABSTRACT This device is an improvement over the conventional Stirling cycle engine where the so called hot" and Appl. No.1 37,749

52 us. 60/517, 60/524 51 Int. F02g 1/04 58 Field ofSearch..................... 60/517, 524; 62/6 Cold cylmders are mounted m a V-wnfiguramn- The improvement comprises the addition of a secondary heat source which cyclically adds heat to the sys- References Cited UNITED STATES PATENTS tem via a third displacement piston communicating with the regenerator.

60/24 60/24 1 Claim, 4 Drawing Figures PATENIEB IIBV 5 I874 INVENTOR.

STERLING PROCESS ENGINES This invention is an improvement in the conventional Stirling cycle as described in the patent to DeBrey et al., US. Pat. No. 2,616,248. In Stirling engines as that disclosed by DeBrey, the hot cylinder, where expansion occurs, and the cold" cylinder, where compression occurs, are mounted in a V-configuration. Power from the expansion cylinder is transmitted via conventional piston rods and a connecting arm to cyclically drive the cold compression piston.

This invention is based on the appreciation that very often auxiliary heat sources are available for use in an engine. In a Stirling engine as that disclosed by Brey et al. and others of its kind, the only consumption of energy, i.e., external heat input, occurs at one stage of the engine, that is, prior to the gass entry into the expansion cylinder. It is noted that conventionally the cold compressed gas is heated in a regenerator prior to the heating stage. However, the regenerators heating ability is limited by the fact that its source of heat is the heat liberated by the working gas after its expansion. Hence, the prior art has here before supplied external energy/heat input at only one stage of the cycle.

It is the object of this invention to provide a Stirling cycle engine in which heat from an external heat source is added to the working gas at two stages of the cycle.

It is also the object of this invention to provide a Stirling engine in which an auxiliary source of heat may be beneficially and economically employed.

The invention will be described more fully with reference to the drawing.

FIG. I is a modified Stirling cycle engine in accordance with the invention.

FIGS. 2-4 are graphs depicting various operating parameters and will be discussed in more detail below.

Now turning to FIG. 1 of the drawing. L is a general designation for the hot-expansion side of the present Stirling cycle engine. As is conventionally known, the working gas must receive energy, in the form of heat, to elevate its temperature and pressure, prior to the expansion step. Piston 5 is the power piston operatively connected to the power output means via a piston rod 6 and a connecting arm 1. The rod 6 is pinned at 3 to the arm 1 in a well known manner. Shown schematically as a source of heat/energy input are fluid conduits and 21, which as illustrated deliver a hot fluid about the hot-side or hot cylinder L to deliver heat to the working gas prior to the expansion step. Obviously this heating step can be carried out by any known and conventional manner.

On the side opposite the expansion cylinder is the cold-compression side of the engine shown generally at R. Piston 7 is slidably mounted in cylinder 16. Conduits l8 and 19 are shown schematically as delivering cold fluid for cooling the working gas either prior to or during the compression step. While conduits l8 and 19 are shown as the cooling means, obviously any known and conventional cooling means may be employed. The

the crank shaft through an appropriate connection at 2 as well as power to drive the compression piston.

The hot-side of the engine, L, is connected to the cold side through an appropriate fluid conduit. In a conventional manner a regenerator structure, designated REG is mounted in said fluid conduit.

Thus far, the structure described is well known in the art as illustrated by the Brey Stirling cycle engine, described in US. Pat. No. 2,616,248. The operation of the structure as set forth up to now is substantially that of a conventional Stirling cycle engine. The working gas is heated and expanded in the hot side of the engine and is then transferred to the cold-side of the engine. During the transfer from the hot-side to the cold-side, the working gas gives off heat to the regenerator. The gas is then cooled and compressed on the cold side of the engine; and on return to the hot side, the gas absorbs heat from the regenerator.

The novelty or improvement of this invention resides in the fact that a third piston, designated at M, is mounted in cylinder 9 and thus, as seen in FIG. I, the regenerator is in fluid communication with this structure. The piston M is connected via suitable linkage to the connecting arm 1. While it is shown that the connecting arm is directly connected to the piston M, obviously any suitable linkage can be employed. The movement of the power piston 5, drives the displacement piston M in an oscillating manner similar to the movement of the compression piston 7. The novel aspect of this device is that above the displacement piston M, is a heating means, designated by the elements l0, l2, l4 and 15. The said elements constitute a means whereby heat/energy from an auxiliary heat source can be delivered to the system. In FIG. 1, the auxiliary heating means is shown as a cable 12 consisting of a steel sheath l5 and a lead core 14 which delivers heat to a grid 10. Obviously, however, any known and suitable means can be employed to deliver heat to the space above the displacement piston M. Working gas above the piston M is cylically heated and cylically driven into heat exchange with the regenerator. Thus the regenerator receives first, heat as the working gas is transferred from the hot-side to the cold-side of the engine, and then receives heat from an auxiliary external source as the displacement of piston M drives the gas above it into heat exchange with the regenerator. As the working gas is then transferred from the cold side to the hot side, it is preheated in the regenerator by an incremental amount over that of the prior art, due to the auxiliary heat source.

It should be noted that the term auxiliary heat source is used here to describe any source of heat that one finds economical to employ. For example, in a conventional fuel burning boiler, the flue gases existing from the boiler usually pass over an element known as an economizer. By way of illustration, the heat from such an element as an economizer could be used as an auxiliary heat source.

The operation of the device is believed to be selfevident to those skilled in the art. The cycle of the working gas proceeds exactly as any Stirling cycle engine with the exception that more heat is delivered at the regenerator stage than would normally be the practice. This enables less heat to be added at the hot-side of the engine, thus making a more economical Stirling cycle engine. Furthermore, by adding heat at the regenerator stage, auxiliary heat sources, which heretofore may have gone wasted, can now be economically employed.

FIG, 2 is a P-V diagram of the working gas as it goes through a complete cycle. From point 3c to point 4a is the expansion or power stroke; 4a to la to 2b are the cooling and compression steps; and finally from 2b to 3c are the preheating (in the regenerator) and final heating steps.

FIG. 3 is a graph showing the relative positions of the three cylinders during one complete cycle of the engme.

FIG. 4 is a graph of the additive displacements of the three cylinders. It is believed that when the curve of the additive displacements of the three cylinders is represented by a smooth sinusoid, optimum results are obtained. However, the phase relationships of the three pistons remains a matter of design for those skilled in the art.

What is claimed is:

l. A hot-gas reciprocating engine having a closed thermodynamic cycle, comprising a first cylinder enclosing a hot space, said hot space receiving heat from a first source of external heat, a second cylinder enclosing a cold space, means connecting said hot and cold spaces, a regenerator interposed in said connecting means, a third cylinder with a displacer piston therein. a second source of external heat supplying heat to the space above said displacer piston, means connecting said space above the displacer piston to the regenerator whereby heat from the second external source of heat is intermittently supplied to the regenerator, said aforementioned three pistons having their center lines converging to a substantially single point wherein said three pistons are operatively connected to a common connecting arm means. 

1. A hot-gas reciprocating engine having a closed thermodynamic cycle, comprising a first cylinder enclosing a hot space, said hot space receiving heat from a first source of external heat, a second cylinder enclosing a cold space, means connecting said hot and cold spaces, a regenerator interposed in said connecting means, a third cylinder with a displacer piston therein, a second source of external heat supplying heat to the space above said displacer piston, means connecting said space above the displacer piston to the regenerator whereby heat from the second external source of heat is intermittently supplied to the regenerator, said aforementioned three pistons having their center lines converging to a substantially single point wherein said three pistons are operatively connected to a common connecting arm means. 